1. Field of the Invention
The present invention relates to a vibration power generation device that converts vibration energy of a vibrating member to electrical energy using a power generating element, and to a sensor device, a vehicle-use light emitting device, and a building-use light emitting device using the same.
2. Description of the Related Art
Conventionally, devices including sensor devices, vehicle-use light emitting devices, building-use light emitting devices or the like that detect various types of physical amount need to be supplied electric power required for their operation from an external power supply such as a battery, commercial power, or the like through a power feeder.
Incidentally, the sensor devices include a pressure sensor for seat or the like as disclosed in Japanese Unexamined Patent Publication No. JP-A-2013-147161. Further, for automobiles, for example, there are not a few cases where the number of sensors mounted thereon exceeds 100, including various types of mechanical sensors, electromagnetic sensors, temperature sensors, optical sensors, and chemical sensors. Also, the vehicle-use light emitting devices include a corner pole and a side mirror light as respectively disclosed in Japanese Unexamined Patent Publication No. JP-A-2005-067365 and Japanese Unexamined Patent Publication No. JP-A-8-104170, or the like, many of which are to be mounted onto members constituting the end of the vehicle in particular. Moreover, the building-use light emitting devices include a light emitting device or the like that illuminates a stairway of a house, as disclosed in Japanese Patent No. JP-B-4290690.
However, with the sensor device or the light emitting device for automobiles for example, since the number of the sensor devices is significant, and many light emitting devices are mounted on near the end of the vehicle body, and so on, arranging the power feeder from the battery may lead to increase in weight due to a great deal of total extension of the power feeder, making it difficult to avoid an adverse effect on mileage or traveling performance. Meanwhile, with the building-use light emitting device, since it is general to emit a light using commercial power, the device may become useless during power outage. Especially during the disaster, there was a problem that the stairway and the corridor used as an evacuation passage are not illuminated, making it difficult to ensure safety.
It would be conceivable to utilize a small built-in battery such as a button battery, a power generation device using a solar panel, or a rotary power generation device disclosed in Japanese Unexamined Patent Publication No. JP-A-2009-254163. Also, as described in JP-B-4290690 mentioned above, it would be conceivable to generate electric power by deforming a flexible step tread by weight of the walker acting thereon, and applying the deformation of the step tread to a piezoelectric element.
However, the small built-in battery has the problem of cumbersome in maintenance because the battery needs to be frequently changed, and the solar panel has the problem that equipment involving storage batteries and a control device may become large-scale and risk of damage may also be significant. In addition, since the use of the rotary power generation device described in JP-A-2009-254163 is limited to high-speed rotating parts such as connecting rods of an internal combustion engine in the first place, range of uses therefor may be narrow, posing a problem of difficulty in use. Furthermore, the use of the power generation device using the step tread disclosed in JP-B-4290690 is limited to the walking region of buildings, and in addition to that, the tread of the walking region is made flexible, thereby giving discomfort to walking sense. Additionally, degree of freedom in designing may be considerably restricted, posing a problem of an adverse effect on the design of the building.
Accordingly, to handle the high demand for energy saving in recent times, in Japanese Unexamined Patent Publication No. JP-A-2011-152004, power generation devices have been proposed that convert vibration energy to electrical energy. However, with the power generation device described in JP-A-2011-152004, the piezoelectric vibrating body is a one-degree-of-freedom vibration system for which the mass member is elastically supported by the spring member, so for vibration input of a frequency that is off from the natural frequency of the vibration system, there is the risk of not being able to generate sufficient deformation of the spring member, and not being able to effectively obtain power.
Meanwhile, U.S. Publication No. US 2013/0320807 discloses a vibration power generation device including a base member disposed above a vibrating member while extending in the horizontal direction, a spring elastically supporting the base member, and a power generating element extending on the base member in the horizontal direction while being capable of bending and vibrating in the vertical direction, wherein the power generating element is supported by the base member. Besides, International Publication No. WO 2013/024848 discloses a vibration power generation device including a retaining frame to be attached to a vibrating body, a support frame of rectangular frame shape elastically supported by the retaining frame, a vibration plate projecting inward from the peripheral wall of the support frame, and a power generating element mounted onto the vibration plate. Employing such vibration power generation devices makes it possible to reduce or obviate power supply from the outside.
However, both of the vibration power generation devices disclosed in these US 2013/0320807 and WO 2013/024848 may suffer from the problem of finding it still difficult to stably and efficiently realize desired power generation at the time of vibration input.
Extensive review and the tests by the inventors have shown a newly notified problem that it is difficult to stabilize the state of deformation of the power generating element caused by vibration input. Specifically, for the power generating element or the piezoelectric element, the direction of vibration that contributes to power generation is determined. On the other hand, the direction of vibration of the base member or the retaining frame elastically supported by the vibrating member is difficult to be determined. Therefore, when the base member or the retaining frame vibrates in the direction that does not contribute to power generation due to vibration input from the outside, a variety of vibration deformations such as oscillation (pitching), torsion, prizing or the like will arise in the power generating element or the piezoelectric element. Consequently, their vibration deformation becomes unstable, posing a problem of difficulty in stably obtaining desired power generation effect.